1. Field of the Invention
The present invention relates to a frequency generator, and more particularly, to a frequency generator that uses one oscillator and includes frequency dividers and a feedback circuit to output a frequency signal in a plurality of domains.
2. Description of the Related Art
Wireless transceivers basically require local oscillator (LO) signals. Broadband characteristics are one of the most important characteristics of LO that have been required these days.
In order to satisfy the broadband characteristics of the LO, capacitor banks may be generally used. When a required band is less than ±15% (30% in total) on the basis of a center frequency, one LC tank and an additional capacitor may be used according to an on and off operation without phase noise. This is a limitation occurring due to a trade-off between the phase noise and tuning range.
However, when the tuning range exceeds 30%, it is difficult to satisfy the broadband characteristics and low-phase noise characteristics at the same time.
Among methods of obtaining broadband characteristics, one is to use a plurality of LC tanks. According to this method, it is possible to obtain a desired tuning range without causing deterioration in phase noise characteristics. For example, when three voltage control oscillators each having a tuning range of 30% are used, a tuning range of 90% can be theoretically obtained. Even when there is a margin in consideration of a process variation, a tuning range of approximately 70% or more can be obtained.
However, since an inductor generally occupies an area of the VCO at a ratio of 50% or more, when the plurality of LC tanks are used, a chip size increases due to the size of the inductor. Therefore, it is difficult to reduce the size of the VCO, and manufacturing costs increase.